The invention relates to an active matrix display device comprising an electro-optical display medium between two supporting plates, a system of pixels arranged in rows and columns, with each pixel being formed by picture electrodes provided on the facing surfaces of the supporting plates, and a system of row and column electrodes for presenting selection and data signals by means of which a range of voltages dependent on the electro-optical display medium can be presented across the pixels for the purpose of picture display, said device comprising means for applying, prior to selection, an auxiliary voltage across the pixels, which auxiliary voltage is beyond or on the edge of the voltage range to be used for picture display.
A display device of this type is suitable for displaying alphanumerical information and video information.
Such a display device is described in U.S. Pat. No. 5,032,831 issued Jul. 16, 1991 filed by the Applicant. In this display device, asymmetrical non-linear switching elements are used for applying voltages across the pixel. In one of the embodiments shown, both the picture display voltage and said auxiliary voltage are presented by means of a zener diode, which is operated in the breakdown mode for presenting the auxiliary voltage.
The technologies which are used for realizing active matrices of switching elements for liquid crystal devices (amorphous silicon, polycrystalline silicon technology) are, however, generally less suitable for realizing zener diodes with a reproducible current-voltage characteristic in the forward direction. Moreover, the light sensitivity, particularly of amorphous silicon, is found to be detrimental.